deploy golang app on docker from ubuntu image (multistage)

Question

using cmd docker compose up inside testdocker folder.

getting below error

here is my dockerfile

# golang base image
FROM golang:1.19-alpine as golangBase
RUN mkdir /app
ADD . /app
WORKDIR /app
RUN go mod tidy && go build -o handlerBuild main.go

FROM ubuntu:latest
RUN mkdir /app
WORKDIR /app
COPY --from=golangBase /app .
ENTRYPOINT [ "/app/handlerBuild" ]

here is my docker-compose.yml

having file structure like below /testdocker

/testdocker/main.go

/testdocker/go.mod

/testdocker/dockerfild

/testdocker/docker-compose.yml

Edit: found the solution here, needed flag CGO_ENABLED=0, while building. Go-compiled binary won't run in an alpine docker container on Ubuntu host

For starters, you're building on Alpine but running on Ubuntu; this is a problem because binaries built on Alpine don't work in most other Linuxes. Also the usual reason for a multistage build is to have a smaller final image, both in size and attack surface. Additionally, your COPY in the ubuntu image is incorrect as pointed out in Campbell's answer. — user5774952
– user5774952, Commented Dec 16, 2022 at 4:39

Campbell · Accepted Answer · 2022-12-16 04:30:54Z

1

I think that when you COPY --from=golangBase /app . from golangBase, because golangBase already has WORKDIR app, Docker tries to copy from /app/app on golangBase (resulting in a file not found error).

Can you try COPY --from=golangBase . .? Additionally, because you set WORKDIR app on the ubuntu image, I think your entrypoint should just be ENTRYPOINT ["/handlerBuild"]. In other words, you can think of WORKDIR appas telling the Docker imagecd appso all commands thereafter should be run relative to the/app` path.

Unrelated note: I'm pretty sure WORKDIR app creates the directory app and also adds it. So instead of

RUN mkdir /app
ADD . /app
WORKDIR /app

I'm pretty sure you could just put

WORKDIR /app

and have the same effect. Correct me if I'm wrong though — I couldn't actually run the Docker build commands because I don't have your source code.

edited Dec 16, 2022 at 4:30

answered Dec 16, 2022 at 4:28

Campbell

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5 Comments

patabhu Over a year ago

did everything you said, but still its not working. now i am getting error like Error response from daemon: failed to create shim task: OCI runtime create failed: runc create failed: unable to start container process: exec: "handlerBuild": executable file not found in $PATH: unknown. if i just change ubuntu:latest to alpine:latest It works, but we need ubuntu image only.

patabhu Over a year ago

main.go just contains a http listerner on 8081

Campbell Over a year ago

My bad can you try ENTRYPOINT ["./handlerBuild"] instead? I forgot to include the leading .

Campbell Over a year ago

Actually I just tried with an example go program locally and ENTRYPOINT ["./app/handlerBuild"] should do the trick

Runsis Over a year ago

thanks for this! you helped me a lot

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